GLOSSARY. 361 
a Univalve Mollusc is closed when the animal has retired within it; 
also the chain of flat bones which covers the gills in many fishes. 
OPHIDIA(Gr. ophis, aserpent). The order of reptiles comprising the Snakes, 
OPHIOMORPHA (Gr. ophis, a serpent ; morphe, shape). The order of _Am- 
phibia comprising the Cecilie. 
OPHIUROIDEA (Gr. ophis, a serpent ; ow7'a, tail; eidos, form). An order of 
Lichinodermata, comprising the Brittle-stars and Sand-stars. 
OPISTHOCELOUS (Gr. opisthen, behind; koilos, {hollow). Applied to ver- 
atte the bodies of which are hollow or concave behind, and conyex in 
ront. 
ORAL (Lat. os, the mouth). Connected with the mouth. 
ORTHOPTERA (Gr. orthos, straight; pteron,’a wing). An order of Insects. 
OscuLa (Lat. diminutive of os, mouth), The large apertures (‘‘ exhalant 
apertures ”) by which a sponge is perforated. 
OsTRACODA (Gr. ostrakon, a shell; eidos, form). An order of small Crus- 
taceans which are enclosed in bivaive shells. , 
OVIPAROUS (Lat. ovwm, an egg; pario, I bring forth). Applied to ani- 
mals which bring forth eggs, in contradistinction to those which bring 
forth their young alive. 
OVIPOSITOR (Lat. ovum, an egg; pono, I place). The organ possessed by 
some insects, by means of which the eggs are placed in a position suit- 
able for their development. 
Ovisac. The external bag or sac in which certain of the Invertebrata 
carry their eggs after they are extruded from the body. 
OVO-VIVIPAROUS (Lat. ovum, an ege; vivus, alive; pario, I bring forth). 
Applied to animals which retain their eggs within the body until they 
are hatched. 
Ovum (Lat. an egg). The germ produced within the ovary, and capable 
under certain conditions of being developed into a new individual. 
PACHYDERMATA (Gr. pachus, thick; derma, skin). An old Mammalian 
order, constituted by Cuvier for the reception of the Elephant, Rhino- 
ceros, Hippopotamus, &Xc. 
PALLIAL. Connected with the mantle or “‘ pallium.” 
Patuium (Lat. a cloak). The ‘‘mantle” of the Mollusca. 7 
Patri (Lat. palpo, I touch). Processes supposed to be organs,of touch, 
developed from certain of the organs of the mouth in various Articulate 
animals, and from the sides of the mouth in the Bivalve Molluscs. 
PaPiLLA (Lat. for nipple). A minute soft prominence. 
PARAPODIA (Gr. para, beside ; podes, feet). The lateral locomotive pro- 
cesses or ‘‘ foot-tubercles”’ of many of the Annelida. ; 
PARIETAL (Lat. paries, a wall). Connected with the walls of a cavity or 
of the body. ‘ 
PARIETO-SPLANCHNIO (Lat. paries, a wall; Gr. splagchnon, an internal 
organ). Applied to one of the nervous ganglia of the Mollusca, which 
supplies the walls of the body and the viscera. } 
Patacium (Lat. the border of a dress). Applied to the expansion of the 
integument by which Bats, Flying Squirrels, and other animals support 
themselves in the air. 
PECTORAL (Lat. pectus, the breast). Connected with the chest. ‘ 
PEDAL (Lat. pes, the foot). Connected with the foot ; generally used in 
connection with the Mollusca. f a 
PEDICELLARIA (Lat. pedicellus, a louse). Curious appendages found in 
many Echinoderms, attached to the surface of the body, and resembling 
a little pair of pincers supported on a stalk. : 
PEDIPALPI (Lat. pes, foot; palpo, I feel). An order of Arachnida, com- 
prising the Scorpions, &c. 
